The main scale reading of a vernier calipers (1 M.S.D. = 1 mm) having least count 0.01 cm ofr the internal and external diameters of a hollow tube are 11 mm and 12 mm. the minimum thickness of the tube is _________.
A. 1 mm
B. 0.1 mm
C. 0.05 mm
D. 0.5 mm